On Sat, Oct 12, 2024 at 09:48:57AM +0100, Andrew Cooper wrote: > On 12/10/2024 5:09 am, Josh Poimboeuf wrote: > > For x86-64, the barrier_nospec() in copy_from_user() is overkill and > > painfully slow. Instead, use pointer masking to force the user pointer > > to a non-kernel value even in speculative paths. > > > > Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org> > > You do realise mask_user_address() is unsafe under speculation on AMD > systems? > > Had the mask_user_address() patch been put for review, this feedback > would have been given then. > > > AMD needs to arrange for bit 47 (bit 58 with LA57) to be the one > saturated by shifting, not bit 63.
Ok... why? -- Josh
